Switching elements are an important feature of many optical communication systems. Herein we are using the term "switching element" broadly, to include any element that changes, in response to a control stimulus, the characteristics of an optical transmission path.
Examples of switching elements are elements that direct signal radiation (herein electromagnetic radiation frequently is referred to as "light", regardless of wavelength) to a selected one of a multiplicity of optical waveguides (1.times.N switch; N.gtoreq.1), or elements that either transmit or reflect the light, depending on the control stimulus. More generally, switching elements are elements that cause a change in amplitude, frequency or polarization of the signal radiation in response to a change in the control stimulus.
Although various types of switching elements are known, it would be of interest if still more such elements were available to the designers of optical fiber communication systems, to facilitate optimization of the systems in terms of performance as well as cost. This application discloses a family of novel switching elements, and articles and systems (collectively "articles") that comprise the elements..
The photostrictive effect is known. It is a phenomenon in which strain is induced in a sample of material when the sample is illuminated. See, for instance, K. Uchino et al., "Ferroelectrics", Vol. 64, pp. 199-208, Gordon and Breach, 1985, and K. Uchino, MRS Bulletin, Vol. 18(4), p. 42 (April 1993), both incorporated herein by reference. See also the abstract of T. Sada et al., J. of the Ceramic Society of Japan, Vol. 95 (5), p. 545 (1987), also incorporated herein by reference.
U.S. Pat. No. 5,502,781, which is also incorporated herein by reference, discloses integrated optical switching elements which utilize a magnetostrictively, electrostrictively or photostrictively induced stress to alter the optical properties of a planar optical waveguide. The stress-inducing material typically is in the form of a patterned thin film that overlies the planar waveguide. Such switching elements are relatively costly, and typically require coupling of the planar waveguide to optical fiber, with attendant significant insertion loss. The herein disclosed photostrictive switching elements typically can be produced relatively inexpensively and generally do not require fiber-to-planar-waveguide coupling.